This section provides background information related to the present disclosure which is not necessarily prior art.
Torque clutch assemblies are commonly used in vehicle transmissions to shift into a forward gear, to shift between different forward gears, or to shift into a reverse gear. As a shift is being effectuated by the transmission, the torque clutch assembly selectively supplies torque from a prime mover, such as an engine, to one or more gears of the transmission. Because the torque clutch assembly can decouple the one or more gears of the transmission from the prime mover and can provide limited slip between the one or more gears of the transmission and the prime mover, shifts can be accomplished without stalling the engine and/or binding the transmission.
The torque clutch assembly may generally include a clutch housing and a shaft that is disposed within the clutch housing. A clutch pack may be disposed radially between the clutch housing and the shaft that selectively couples rotation of the clutch housing and the shaft. The clutch pack may include various combinations of friction plates that transfer torque between the clutch housing and the shaft when the friction plates are pressed together by a clutch actuator. While the friction plates are rotatably coupled to either the clutch housing or the shaft, they are moveable in a longitudinal direction with respect to the clutch housing and the shaft. A backing plate may be provided at one end of the clutch pack that is retained on either the clutch housing or the shaft. Longitudinal movement of this backing plate relative to the clutch housing and the shaft may be limited such that the backing plate acts as a stop for the friction plates when the friction plates are pushed towards the backing plate by the clutch actuator. A reaction plate may be provided at an opposite end of the clutch pack. Like the friction plates, the reaction plate is moveable in the longitudinal direction with respect to the clutch housing and the shaft. The clutch actuator may be configured to apply pressure to the reaction plate such that the friction plates are squeezed between the reaction plate and the backing plate. Accordingly, actuation of the clutch actuator longitudinally compresses the clutch pack.
Depending upon different power flows through the transmission and different levels of torque multiplication occurring before the torque clutch assembly (i.e. torque multiplication occurring at one or more points positioned between the prime mover and the torque clutch assembly), different torque transmission values through the torque clutch assembly may be desirable. Traditionally, different torque transmission values transmitted through torque clutch assemblies were achieved by varying the pressure that the clutch actuator applies to the reaction plate. Essentially, by varying the clamping (i.e. squeezing) force applied to the friction plates by the reaction plate and the primary backing plate, different torque transmission values could be achieved by increasing or decreasing the amount of slip between the friction plates, the reaction plate, and the backing plate. This option has its drawbacks, however, since the friction plates are typically torque sensitive in only a very narrow range of applied pressure. As a result, the pressure that the clutch actuator applies to the reaction plate can only be varied so much before clutch operation suffers making it difficult to produce a clutch assembly that is effective at both high and low torque transmission values.